The Journal of Pediatrics
Volume 149, Issue 1 , Page 141, July 2006

Humidified air appears to be of no benefit in treating moderate croup

University of Michigan, Ann Arbor, MI

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Scolnik D, Coates AL, Stephens D, Da Silva Z, Lavine E, Schuh S. Controlled delivery of high vs low humidity vs mist therapy for croup in emergency departments: A randomized controlled trial. JAMA 2006;295:1274-80 

Question Among children with moderate to severe croup who were admitted to the emergency department, does 100% humidity or 40% humidity via nebulizer or blow-by humidity result in improved croup symptoms?

Design Randomized, single-blind, controlled trial.

Setting Tertiary care pediatric emergency department in Toronto, Ontario.

Participants A convenience sample of 140 previously healthy children 3 months to 10 years of age with Westley croup greater than 2 (scoring system range, 0-17); 21 families refused participation.

Intervention Thirty-minute administration of humidity using traditional blow-by technique (commonly used placebo, n = 48), controlled delivery of 40% humidity (optimally delivered placebo, n = 46), or 100% humidity (n = 46) with water particles of mass median diameter 6.21 μm.

Outcomes A priori defined change in the Westley croup score from baseline to 30 and 60 minutes in the 3 groups.

Main Results Groups were comparable before treatment. At 30 minutes, the difference in the improvement in the croup score between the blow-by and low-humidity groups was 0.03 (95% confidence interval [CI], −0.72 to 0.66), between low- and high-humidity groups, 0.16 (95% CI, −0.86 to 0.53), and between blow-by and high humidity groups, 0.19 (95% CI, −0.87 to 0.49). Results were similar at 60 minutes. Differences between groups in pulse and respiratory rates and oxygen saturation changes were insignificant, as were proportions of excellent responders; proportions with croup score of 0 at study conclusion; and proportions receiving dexamethasone, epinephrine, or requiring additional medical care or hospitalization.

Conclusions One hundred percent humidity with particles specifically sized to deposit in the larynx failed to result in greater improvement than 40% humidity or humidity by blow-by technique. This study does not support the use of humidity for moderate croup for patients treated in the emergency department.

Commentary This is probably the most well-planned and well-executed study to date on the topic of humidity and croup.1, 2, 3, 4 However, the failure to disprove the null hypothesis does not warrant an outright dismissal of the use of humidified air for all croup patients.5 First, the study is generalizable only to patients presenting to an emergency department with moderate disease and who already reside in a moderately humid environment.6 In addition, there was arguably no true control group, in the sense that the low-humidity group received blow-by air at 40% humidity, which is, per the authors’ report, an ambient level of outdoor humidity. For decades, it has been the common wisdom to place a croupy child outdoors to relieve his or her symptoms. Conceivably, a steady stream of moderately humid air is beneficial, and the addition of more humidity has no effect.

The study succeeds in highlighting a sometimes striking difference between the standard of care and evidence-based practice. We use humidified air because it is a practice passed along from generation to generation of physicians. If nothing else, it serves as “something to do” while a moderately ill child declares herself further. Scolnik et al do point to 2 studies that indicate that small particles of aerosolized water, of the sort that one can find in blow-by humidified air, tend to deposit in the lower airway and may cause bronchospasm. Nonetheless, the likelihood that children will incur harm from blow-by humidified air is small, particularly because none of the studies investigating the use of aerosolized humidity in croup have found this to be the case. While this article provides food for thought, it does not yet warrant a change in practice. What is needed is a study that compares a period of observation to the use of humidified air in children with moderate croup, with the thoughtful eye to detail displayed in this study.

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References 

  1. Neto GM , Kentab O , Klassen TP , Osmond MH . A randomized controlled trial of mist in the acute treatment of moderate croup . Acad Emerg Med . 2002;9:873–879
  2. Westley CR , Cotton EK , Brooks JG . Nebulized racemic epinephrine by IPPB for the treatment of croup—a double blind study . Am J Dis Child . 1978;132:484–487
  3. Bourchier D , Dawson KP , Fergusson DM . Humidification in viral croup (a controlled trial) . Aust Paediatr J . 1984;20:289–291
  4. Skolnik NS . Treatment of croup (a critical review) . Am J Dis Child . 1989;143:1045–1049
  5. Henry R . Moist air in the treatment of laryngotracheitis . Arch Dis Child . 1983;58:577
  6. Fielder CP . Effect of weather conditions on acute laryngotracheitis . J Laryngol Otol . 1989;103:187–190

PII: S0022-3476(06)00355-6

doi:10.1016/j.jpeds.2006.04.029

The Journal of Pediatrics
Volume 149, Issue 1 , Page 141, July 2006

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